Such an actuator is known from the unpublished DE 10 2011 078 525 A1, wherein the holding element is a permanent magnet that is arranged between the housing and the magnetic armature and holds the magnetic armature and the pin at rest until the magnetic force threshold is exceeded. The actuator is part of a valve train of an internal combustion engine with variable-lift gas-exchange valve actuation. The variable lift is generated by the camshaft that comprises a carrier shaft and a cam piece locked in rotation on this carrier shaft and arranged so that it can move between axial positions. The cam piece has at least one cam group of directly adjacent cams with different lifts and an axial slotted piece in which the pin of the actuator is coupled, in order to shift the cam piece on the carrier shaft between the axial positions and thus to switch the instantaneous cam lift pick-off from one cam to another cam.
The switching procedure should be precise and reproducible at the highest possible switching rotational speed and accordingly within the shortest amount of time and should be completed for all cylinders of the internal combustion engine within one work cycle. Ideally, all of the actuators are sufficiently quick and have no time variance with respect to the movement behavior of the pin moving out from the housing. In reality, however, the precise timing of the switching process is negatively affected by the varying extension movement of the pin due to production tolerances and the wear of the actuator components, as well as the large operating temperature range that causes not only varying friction relationships on the oiled actuator components, but also varying electrical resistance in the magnetic coils.
In the case of the variable lift valve train, the insufficiently precise timing of the actuator can lead to unacceptable incorrect switching of the cam pieces on the carrier shaft.